SEDIMER (Lahars risks on the Merapi Volcano, Java, Indonesia)
The 2010 Merapi eruption has demonstrated that downstream areas can be impacted quickly and with economically devastating consequences by lahars and flooding in response to extreme sediment loading of watersheds by ashfall and pyroclastic flows. This eruption thus provides a unique opportunity to gather data on the factors influencing the generation, dynamics, rates and magnitudes of post-eruptive sedimentation processes in response to large-scale eruptions in a humid tropical climatic environment. It also allows us to quantify in fine detail the human and economic impacts of the lahars and use the results as indicators of the vulnerability of local populations to natural hazards.
We propose a collaborative study gathering experienced international experts and young scientists from seven countries including Indonesia to determine what happened in 2010 and what is likely to happen in the next three years in the river valleys downstream of Mt Merapi.
We plan to complete a database on lahar occurrence and related disasters, to identify the sediment sources, to study the lahar dynamics and geomorphic impacts with implications for risk prevention. We will calculate the economic impacts (loss and benefits) caused by lahars and assess risk perception among local residents. This multi-disciplinary study will rely on a combination of innovative methods using high-tech instrumentation: optical and high-resolution radar remote sensing; hydrological monitoring based on various seismic and acoustic sensors, video footage of lahars in motion including nocturnal recording by infrared cameras; up-to-date modeling techniques; an innovative protocol for studying lahar depositional processes; and widespread surveys among risk managers and residents.
In the shorter term, a better understanding of what is currently happening in the rivers downstream of the Merapi volcano can inform public policy with respect to rebuilding or relocating some villages and other facilities. In the longer term, the evidence gained can guide land-use and emergency-response planning in the vicinity of this volcano but also in other similar settings where sedimentation hazards during and following future eruptions are significant. We hope to improve our ability to predict the location and magnitude of downstream impacts on river channels. Results of our study could assist Indonesian officials in public policy decision-making with regard to:
(i) rebuilding, or not, some villages at their present sites,
(ii) how long river channel instability may persist,
(iii) where safer sites may occur if village relocation is decided,
(iv) what are individual behavior patterns and what should be done to improve or modify these behaviors (e.g., community-based warning system for self-evacuation).
The SEDIMER Interdisciplinary project will contribute to strengthening links between international networks working on lahars, regional networks of scientists from various institutions, field operatives, and populations at risk.